Thiadiazinones for stimulating cardiac activity

Abstract

This invention relates to N-phenylpyridone derivatives which have inotropic, vasodilator and bronchodilator activity. A compound of the invention is 5-methyl-6-[4-(4-oxo-1,4-dihydropyridin-1-yl)phenyl]-4,5-dihydro-3(2H)pyridazinone.

What is claimed is: 
     
       1. A compound of the formula (1): ##STR38## or a pharmaceutically acceptable salt thereof, wherein: A is a group of sub-formula (a) or (b): ##STR39## X is sulphur; R 2  is hydrogen or methyl; Y is sulphur; and   R 3  and R 4  are each hydrogen or R 3  and R 4  together form a methylene group.   
     
     
       2. The compound according to claim 1 wherein: A is a group of sub-formula (a): ##STR40## X is sulphur; R 2  is hydrogen or methyl; and   R 3  and R 4  are each hydrogen.   
     
     
       3. The compound according to claim 2 which is 5-[4-oxo-1,4-dihydropyridin-1-yl)phenyl]-6-methyl-3H,6H-1,3,4-thiadiazin-2-one or a pharmaceutically acceptable salt thereof. 
     
     
       4. The compound according to claim 1 wherein: A is a group of sub-formula (a): ##STR41## X is sulphur; R 2  is hydrogen; and   R 3  and R 4  together form a methylene group.   
     
     
       5. The compound according to claim 4 which is: 7-(4-oxo-1,4-dihydropyridin-1-yl)-9a-methyl-9,9a-dihydroindeno[1,2-e][1,3,4]thiadiazin-2(3H)-one; or   7-(4-oxo-1,4-dihydropyridin-1-yl)-9,9a-dihydroindeno[1,2-e][1,3,4]thiadiazin-2(3H)-one; or a pharmaceutically acceptable salt thereof.     
     
     
       6. The compound according to claim 1 wherein: A is a group of sub-formula(b): ##STR42## Y is sulphur; R 3  and R 4  are each hydrogen.   
     
     
       7. The compound according to claim 6 which is 2-[4-(4-oxo-1,4-dihydropyridin-1-yl)phenyl]-4H,6H-1,3,4-thiadiazin-5-one or a pharmaceutically acceptable salt thereof. 
     
     
       8. A pharmaceutical composition which comprises a compound according to claim 1 and a pharmaceutically acceptable carrier. 
     
     
       9. A pharmaceutical composition according to claim 8 in unit dose form adapted for oral administration. 
     
     
       10. A method for stimulating cardiac activity in a host in need thereof by administration of a non-toxic but effective amount of a compound according to claim 1. 
     
     
       11. A method for effecting bronchodilatation in a host in need thereof by administration of a non-toxic but effective amount of a compound according to claim 1. 
     
     
       12. A method for effecting phosphodiesterase (type III) inhibition in a host in need thereof by administration of a non-toxic but effective amount of a compound according to claim 1. 
     
     
       13. A method for treating congestive heart failure in a host in need thereof by administration of a non-toxic but effective amount of a compound according to claim 1.